Gear inches is an old way of measuring output, the inch part is related to Penny Farthings and the size of their wheels.
Essentially you don't need to worry about understanding it per se, what I would do is go to a site like this one:
https://www.bikecalc.com/gear_inches
I would take an existing bike you own and enjoy riding, then enter in the size of the teeth on your cassette and chainring. This would give you the range of inches you have at the moment, so for example if your small chainring is 36 teeth and the largest cog you have on your cassette is 34, then that gives you a low gear of 30 inches. So you know how this feels to ride and gives you a benchmark for when you input the theoretical values for your new 1x set up as a comparison.
One thing I would also advise, is whichever chainset you go for, I would look for one with a chainring that can be easily changed. I have a Race Face Aeffect chainset, which I can not only change the chainring quickly and easily, but, steel replacement rings are relatively cheap. So I run a 32 tooth ring for normal gravel/trail riding, then when I'm bikepacking I swap it out for a 28 tooth one.
Married to a 11 speed 10 - 42 cassette, the 32 tooth chainring gives me a range of 21 - 90 inches, which is perfect for the gravel trails I encounter daily. The smaller 28 tooth chainring gives me a range of 18 - 78 inches. The 18 inch gear means I can easily climb some real steep off-road climbs fully loaded, the trade of, is the 78 inch top gear means I am not that fast on smooth flat roads and end up spinning my legs at 32 kph at getting no more speed.