Navigate to Services → Squid Proxy Server.

In Logging Settings section:

• Enable Access Logging: Not Checked.

Click Show Advanced Options button at the bottom of the page.

In Custom Options (Before Auth) section:

• Add the following lines:

  logformat squidmimemod %ts.%03tu %6tr %>a %Ss/%03>Hs %<st %rm %ru %un %Sh/%<A %mt %rp %>st "%{Referer}>h"
  
  access_log /var/squid/logs/access.log squidmimemod
  
  logfile_rotate 90