Open up Settings
Choose About your Phone
Look for an option that says 'About Phone' or 'About Device.' On older models, this will be 'Status.'
Check your Model
Google the Model Number
Enter the 5-digit code (with or without the SM- prefix) into Google or similar search engine.
This will show you exactly what Samsung Galaxy model you have so you can choose the right Samsung Galaxy repair for your device.
The above example shows that the Model number G973F is a Samsung S10.