Bearing. For what?

"Mike" it. Most bearings are metric. There are rather special ones that are inch measurements, but these are usually for things like table saws where you have inch measurement blade arbor mounts, etc.

Usually, if you get one measurement accurate, you can find the other without such accuracy. Find a local bearing outfit that has an IBI "International Bearing Interchange." You might even find that online.

such as........

https://www.hchbearingamericas.com/62-series-bearings
https://www.mrosupply.com/blog/ball-bearings-size-chart/
And a 6203 size wise is same as a 203