The mouse pad on my old MAC does not work...How can I transfer files from the old Mac to the new Mac?

Borrowing a mouse is usually the easiest, but you can switch on and use the Mac keyboard as a mouse with the “mouse keys” feature.

… Change Alternate Control Methods preferences for accessibility on Mac - Apple Support

… Control the pointer using Mouse Keys on Mac - Apple Support

… Use your keyboard like a mouse with Mac - Apple Support

Hi Marisa,

I am assuming you mean the trackpad for this response, is this a MacBook? You should be able to use an external mouse (maybe buy one or see if a friend will let you borrow theirs) to take the place of the trackpad and get the transfer taken care of.