Vb6 how to find a record based on multiple id

I have a table in my database based on a multiple ID
FirstID SecondID they are both primary keys I understand the vb find a record with one primary key
I haven't got a clue how to do this with 2 primary keys
I also want to check if the combination of those keys exists
FirstID is an existing key from another table SecondID is the new key
so a get keys like 1.1 1.2 1.3 an so on