Welcome to the forum, Suzi.
While I don't know the exact answer to your question, I can say that it's safer to err on the side of adding more oil to the mixture. If you go with 32:1 that would be pretty safe, IMO.
Did you look for a model number on the trimmer? That would be a good thing to have in any case. If you have that you could Google that number and probably find specs for the trimmer -- including the ratio you're looking for.