How to get key to repair TPB I?

I'm not sure what you mean by TBP I here and there are no key items to get. You can repair your city durability with diamonds after you have been attacked, although you don't need to as it will recover on its own over time.

If you run out of durability on your APC's this will also regenerate over time but you can also use 'wrench' items (tools) to 'repair' then and recover durability. These items are only available to buy with real money though. You can find packages in the shop with the items in them. A short cut to finding them is to tap on one of the barracks buildings in your city and select the repair option. this will show you your APCs with the option to use the items if you have them and a banner at the top with a link to the shop item to buy the 'wrenches'

let us know if this doesn't answer your question.