fix scales

[ycattan]

Fixing scale for microgrammes and scale for "per_m"

1 microgramme = 1e-3 milligramme

1 per_cm = 1e-2 per_m

• [ ] If this PR is a bug fix, the bug is documented in the test suite.
• [ ] Changes were documented in the changelog (pending section).
• [ ] If necessary, changes were made to the documentation (eg new pipeline).

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (c65030a) 96.58% compared to head (bc145b7) 96.58%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #231 +/- ## ======================================= Coverage 96.58% 96.58% ======================================= Files 254 254 Lines 8356 8356 ======================================= Hits 8071 8071 Misses 285 285 ```

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