To find out what model of Samsung phone you own you can either look in Settings or look for it printed on the device.
Settings
Go to Settings > About phone. You should see a model name i.e. Galaxy S20
Printed on the Device
If you look at the back of your device, towards the bottom of the phone Samsung print the IMEI, serial and model numbers on the phone.
If you take the model number which will look something like “SM-G950F” and search for this in Google it’ll tell you what model you have. So for example "SM-G950F" is a Galaxy S8.