What do you do if you no longer have the computer you normally sync too?

It appears you are going to lose everything you have on your iPod.

Allan

Your question and the screenshot imply two separate questions.

If you do not have your original computer then you can only "erase and sync" your iPod Touch. That does exactly what it says, in that order. First it is erased. Then, whatever is on the computer's iTunes Library will be transferred to the iPod.

If you don't want that to happen, don't do it.

You can/could have done:

Syncing to a "New" Computer or replacing a "crashed" Hard Drive: Apple Support Communities

Sync Your iOS Device with a New Computer Without Losing Data - How-To Geek

When you restored the iPod like the articles said the iOS will also be updated.