My blower will not run it just makes a loud humming sound I'm sure I may need to replace it. And I know I can but I don’t know where to start to look for the part new or used

First do the following simple check... spin the blower while it is humming ( be careful.. it may start! ) if it starts now, the problem may be that the capacitor is bad. The capacitor may be checked if you have the proper volt meter and you have electrical knowledge and experience.

It is fairly easy to do a rough check of a capacitor with an ohm meter. Short the capacitor, and remove one lead. Watch the meter reading as soon as you connect the leads. If it jumps up to a high reading and then climbs off scale, likely it is OK. If not, remove it and take it to an electrical or HVAC supply. Let them match it up. A quick easy fix.

If you are unsure about the capacitor, read up on them at https://www.askmehelpdesk.com/heating-air-conditioning/heating-cooling-maintenance-repair-troubleshooting-frequently-asked-questions-58313.html