以下のことで困っています。
ご存知でしたらご教示ください。
よろしくお願いいたします。

やりたいこと

squidを使用したプロキシサーバー構築

--詳細--

squid ver.3.5.28を使用
windows7内で起動
windows7とインターネットとの経路の間に別のプロキシサーバが存在している

①windows7とは別の媒体がsquidのプロキシサーバへhttp通信
↓
②squidのプロキシサーバが別のプロキシサーバに通信
↓
③別のプロキシがインターネットに通信

#今困っていること
①の時点で407エラーとなります。
この場合、どこをどう直せばよいのかよくわからない状況となっています。

↓↓今回しようしたsquid.confはこちらです↓↓

#
# Recommended minimum configuration:
#

auth_param basic program C:/Squid/lib/squid/basic_ncsa_auth.exe C:/Squid/usr/passwd
auth_param basic children 5
auth_param basic realm Squid proxy-caching web server
auth_param basic credentialsttl 2 hours
auth_param basic casesensitive off

# Example rule allowing access from your local networks.
# Adapt to list your (internal) IP networks from where browsing
# should be allowed
#acl localnet src 10.0.0.0/8    # RFC1918 possible internal network
#acl localnet src 172.16.0.0/12    # RFC1918 possible internal network
#acl localnet src 192.168.0.0/16    # RFC1918 possible internal network
#acl localnet src fc00::/7       # RFC 4193 local private network range
#acl localnet src fe80::/10      # RFC 4291 link-local (directly plugged) machines
#acl net src 172.26.53.0/24  
acl localnet src 172.26.53.0/24 

acl password proxy_auth REQUIRED

acl SSL_ports port  443
acl Safe_ports port 80        # http
acl Safe_ports port 21        # ftp
acl Safe_ports port 443        # https
acl Safe_ports port 70        # gopher
acl Safe_ports port 210        # wais
acl Safe_ports port 1025-65535    # unregistered ports
acl Safe_ports port 280        # http-mgmt
acl Safe_ports port 488        # gss-http
acl Safe_ports port 591        # filemaker
acl Safe_ports port 777        # multiling http
acl CONNECT method CONNECT


#
# Recommended minimum Access Permission configuration:
#
# Deny requests to certain unsafe ports
http_access deny !Safe_ports

# Deny CONNECT to other than secure SSL ports
http_access deny CONNECT !SSL_ports

# Only allow cachemgr access from localhost
#http_access allow localhost manager
#http_access allow net 
#http_access deny manager

# We strongly recommend the following be uncommented to protect innocent
# web applications running on the proxy server who think the only
# one who can access services on "localhost" is a local user
#http_access deny to_localhost

#
# INSERT YOUR OWN RULE(S) HERE TO ALLOW ACCESS FROM YOUR CLIENTS
#

# Example rule allowing access from your local networks.
# Adapt localnet in the ACL section to list your (internal) IP networks
# from where browsing should be allowed
#http_access allow localnet
#http_access allow localhost

http_access allow password

# And finally deny all other access to this proxy
# http_access deny all

# Squid normally listens to port 3128
#http_port 3128
#http_port 8080 intercept ssl-bump cert=C:\Squid\etc\ssl\cert.pem generate-host-certificates=on dynamic_cert_mem_cache_size=4MB
http_port 8085

# Uncomment and adjust the following to add a disk cache directory.
#cache_dir ufs /var/cache/squid 100 16 256

# Leave coredumps in the first cache dir
coredump_dir /var/cache/squid

#
# Add any of your own refresh_pattern entries above these.
#
refresh_pattern ^ftp:        1440    20%    10080
refresh_pattern ^gopher:    1440    0%    1440
refresh_pattern -i (/cgi-bin/|?) 0    0%    0
refresh_pattern .        0    20%    4320

logformat squid %ts.%03tu %6tr %>a %Ss/%03>Hs %<st %rm %ru %[un %Sh/%<a %mt %tl %err_code/%err_detail

dns_nameservers 172.26.53.254 8.8.8.8 208.67.222.222

max_filedescriptors 3200

cache_peer 10.100.107.101 parent 8080 0 no-query



never_direct allow SSL_ports

header_replace User-Agent Mozilla/5.0 (Windows NT 6.1; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/74.0.3729.131 Safari/537.36

sslproxy_cert_error allow all
sslproxy_flags DONT_VERIFY_PEER