Confirmations for an address aren't really a thing. Addresses are not confirmed; transactions are. A single address is typically used in multiple transactions: one where the address is used as an output, and one where the first transaction was used as an input. Although it's not a best practice, addresses can even be re-used multiple times.
It looks like this particular address has been used in two different transactions. Once as an output in 00c83c7677d414053488d0b51067feee157a5b82d5acec5bfe8e9c540c11c624, and once as in input in 378f829160cb9c99cc7a8fb1152472b80f0e1ea9c9cc24118dbccc2da72dedcf.
Each of these two transactions returned in the API response has a
block_height value (
489355). That is the block at which the transaction was included. To find how many confirmations each transaction has, subtract the
block_height by the height of the most recently confirmed block, and add 1. So if the current block is
489355, one transaction has 1 confirmation, and the other has 3.