I have my 12 word passphrase and would like to see the contents of my wallet how do I see this wallet on a new app or site?
If you don't care about your privacy, you can always find the associated extended public key (xpub*) and enter it in a blockchain explorer site such as https://www.blockchain.com/explorer.
Here is how a Bitcoin account's (M/44'/0'/0'/) extended public key for a given set of 12 seed words can be computed on a trusted air gapped offline computer that could be operating in a Faraday cage:
% echo "radar blur cabbage chef fix engine embark joy scheme fiction master release" | bx mnemonic-to-seed | bx hd-new | bx hd-private -d -i 44 | bx hd-private -d -i 0 | bx hd-public -d -i 0
Ledger and Trezor devices can be queried to gain access to your xpub key.
Otherwise, just apply the KISS principle and use your wallet application that will naturally provide you with an account balance.