what is the best way to convert old vhs tapes

Basically, you have an analogue source - your VHS tapes - and you need to convert them to a digital source your computer can understand. So you need a gadget for that. Your player connects to the gadget, the gadget to the Mac. Most often recommended is one such as this:

https://www.amazon.com/Canopus-ADVC-100-Advanced-Digital-Converter/dp/B00007L68E

There are less expensive ones, just make sure whatever you choose matches the ports on both the player and the computer.

You can record the coveted signal with iMovie and output the finished movies from that. Then burn them to DVD with an app like Toast.

https://www.roxio.com/en/products/toast/titanium/

many usb tv tuners have support for recording to the computer

many usb tv tuners has support for composite input

that is how I make old vhs tapes into dvds