Replace fan n a MacBook Pro 13 Inch 2017.. Fans are listed on Amazon with an Axxxx number and say mid 2017.. How do i make sure I'm getting the right fan>

You should see the matching Axxxx number next to the serial number etched on the bottom of your MacBook Pro.

The Axxxx numbers follow the chassis specifications, regardless of what processor, RAM, storage are installed.

If the vendor doesn't provide the necessary information or instructions to properly identify the models compatible with their product, then you should steer clear of that vendor. Any reputable vendor will have clear & precise information & details on which exact models a particular item/part is compatible.

FYI, there are only two versions of the 13" 2017 MBPro....one with the Touchbar and one without....the fans are different between those two models. The fans for the 2017 model are the same as for the 2016 model. The 2018 model uses different fans as do the 2015 models.