I cannot connect my Apple Watch 7 to my iPhone 12 mini

Yes you can. What issues you are having connecting watch?

Things to check

Iphone has latest iOS version.

Iphone is nearby watch and connected to wifi.

Watch is charged sufficiently

Use watch app on Iphone to start pairing.

Follow this

https://support.apple.com/en-ca/HT204505

Then you must update the watch,

Click start pairing on iphone watch app.

It will say update watch or exit setup.

Select update watch.

Keep iphone connected to wifi and nearby to watch, keep watch on charger.

Let the update get downloaded. Then it will say preparing then it will install update.

You will see spinning gear all the time on screen. Do it on your free time might take 30 minutes or longer depends on wifi speed.