Can I trade in a Samsung Galaxy?

Yes.

If you want to get an estimate, go to the Smartphone section in the "Select your device to get a trade-in estimate." area of Apple Trade In - Apple

Ijustwanttolookattheforums

They will give a value. They are currently showing $90 for an S9 with 64GB in good condition.

You can trade-in this phone to Apple but as it is a non--Apple product they will not give you anything for it but they will recycle it. You might want to trade it in to a electronics store near you and then use said funds to put towards an Apple device.