3.5"TFTLCD and Adafruit_Fingerprint Mega2560

Fine. Which one? Links to the datasheet of the finger sensor.

That's something to attach first.

Please read the advice, how to post code, in this link: How to get the best out of this forum - Using Arduino / Project Guidance - Arduino Forum

You posted text....

When things don't work the helper question is clear: Post schematics!
Way too often problems are caused by improper powering/wiring.