What is the best gauge wire to use dor this hookup.. I have 10/2 outdoor wire. 30amp 2 pole breaker. Is this what I need?

More importantly, you need an interlock plate for your fuse panel so that the backfed breaker and the main cannot be on at the same time. There has been a suggested reference recently here.

You don't want to electocute a lineman, do you? Your generator can electrify the line to 10,000 volts or more with a transformer acting in reverse.

You also need a generator input connector mounted on the outside of your house.

Even so, you'll need 4 conductor wire from the generator to the input connector, but you may be able to by the cordset.

Inside you'll need 3 conductor with ground.

Alternatively, you can use a transfer switch instead of the interlocking breaker.