how do I get my old apps to my new phone?

Log in to the Apple ID they were purchased with and download them.

For a more robust way of moving from one phone to another, see—>Transfer data from your previous iOS device to your new iPhone, iPad, or iPod touch - Apple Support

Kinda depends.. did you do a backup of your old phone and plan to restore to your new phone? If so, the restore process will take care of this for you.

If you plan to set your phone up from scratch, as long as you sign in with the same Apple ID that you purchased/downloaded your apps with previously, you should be able to go find them and download them.