You can calculate it yourself using ratios in a simple Excel spreadsheet, or use one of the online calculators. This is one of the better ones.
That’s pretty big gearing for mountains for most people (ie unless you are a strong rider). I live in Colorado and have 50-34 and 11-32.
At 34-32, my cadence is 20% higher than it would be at the same speed in 36-28. So 70 rpm in 36-28 would be mid 80s on 34-32.
If you have the $, and will be doing more climbing in the mountains, Probably worth changing your rings, cassette, derailleur and chain.
A cheaper option is to try an 11-32 (or 11-34 if you want to push it) cassette. You might be able to make this work with your existing derailleur and adding a wolftooth roadlink.
You’ll probably also need to lengthen your chain (by maybe 1 inches) to make this work.