Hi Jalor1525,
For paid midi songs you can search in Yamaha's site.
The midi songs contain also lyrics and chord symbols, and they are fine equalized to play on Yamaha keyboards (of course).
https://shop.usa.yamaha.com/en/downloadables/songs/midi.html?p=3DGX-670
Recommended Version XT2
Other Compatible Versions XT XA XG GM
From time to time they have 20% discount. Maybe they have one on Christmas.
For non paid midis you just search on Google the song you are looking for, although they rarely contain lyrics and chord symbols.
Also, they need to be equalized on the keyboard by using the mixing console in order to sound nice.