I had an iphone can i use my sim in a Samsoung Galaxy 8 notes

The phone has been obsoleted by Samsung so you won’t get any security or software updates.

Samsung site says this about the SIM card:

Single SIM model: one nano SIM and one microSD slot (can hold a microSD card up to 512GB)

Dual SIM model: one nano SIM and one Hybrid slot (can hold a microSD card up to 512GB or a nano SIM card)

If the samsung takes a "nano" sized SIM and the SIM is still in service then yes.

We're not samsung experts.