what if I find my password, that I wrote down many years ago, but the PC, and so the wallet is gone. can I use this password on a new wallet.dat and get accseess to my coins ?
It sounds like you are confusing two distinct objects: a password, and a seed phrase.
A password is used to encrypt a file, so that if you have the encrypted file but not the password, you cannot read the file's contents.
A seed phrase is used to derive a master private key that the rest of a wallet's keys will be based upon. So if you have the seed phrase, you can recreate the wallet.
From the sounds of it, you likely have a password that can be used to decrypt a specific wallet.dat file, not a seed phrase. A seed phrase will most commonly be a set of 12-24 words, while a password will be a (hopefully highly entropic) string of characters. If you created the wallet file many years ago, chances are the BIP 39 standard for creating HD wallets from a seed phrase was not widely used yet, furthering my suspicion that you indeed have a password, and not a seed phrase.