Where to put Acl file?

I have an acl item in squid.conf like the following:
-----
acl Valid_Host src HostA HostB
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I want to creat a file to take place of "HostA HostB"
like this:

----
acl Valid_Host src "VHost"
----
My question is where should I put this file.
If I add path to VHost,squid complains error like
"can't find file"
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