If you sent a public key for connection, only the private key associated with it will be able to connect. If you regenerate new keys, it doesn't matter what passphrase you use, it will be different keys. Keys are randomly generated and your passphrase does not impact this, it "only" encrypts your private key at rest so that if someone steals it, it cannot be used without the passphrase.

It is generally advised to create different key pairs for each device and each server to connect to, in this since both termux and connectbot are an your phone you may want to use the same key, or you may generate a new key pair in termux and share the public key again to be authorized to connect with this new private key.

If you want to reuse your old key, you have to find where it currently is and copy it to ~/.ssh/. I would advise to inform ssh how to connect to your server by editing (or creating) the ~/.ssh/config file (you can find the syntax online). It should mention the key to use to connect to your host.