Swap letter and digit runs
Retina, 15 bytes

(\D+)(\d+)
$2$1


This replaces the regex (\D+)(\d+) with $2$1. Let's break that down if you don't know what that means.

The \D means 'match anything that isn't a number'. \d means 'match everything that is a number'. The + sign means 'match this at least once but try to match it as many times as possible'. The brackets define a group. The first group is (\D+) and the second is (\d+)

In the second line we say that we want to put whatever was matched by the second group, followed by whatever was matched by the first group. This effectively swaps the letter and digit runs.

Try it online!