I am thinking about cashing in an annuity and was wondering how much tax I would have to pay, if any?

Without details, it's not possible to provide any useful information. What type/kind of annuity? Your tax rate is also dependent upon many other things such as total income from all sources for the entire tax year. Not all income sources are taxed at the same rate either. One thing you can do is check out TaxCaster at https://turbotax.intuit.com/tax-tools/calculators/taxcaster  It's currently set up for 2022 taxes, but can gen you a *very* rough idea of your tax liability.

The annuity is a traditional IRA 408(b)

You should just use the TaxCaster app referenced above, as nobody here is going to figure you're tax liability for you with any better degree of accuracy.