Do i have to format the samsung 860 EVO external SSD to use as my time machine back up

See the following from Back up your Mac with Time Machine - Apple Support

If the disk you selected isn't formatted as required by Time Machine, you're prompted to erase the disk first. Click Erase to proceed. This erases all information on the backup disk.

It will format it for you and will then do the initial backup. Just plug in your external SSD and follow the instructions in Back up your Mac with Time Machine - Apple Support

USB-C is a port or connector design.

USB 3 is a data protocol.

The following may help: https://www.digitaltrends.com/computing/usb-c-vs-usb-a/

The supplier of the enclosure and Samsung should be your source for information about capabilities of the hardware in question.