Note: if you want to set different units in the same table, you need to use the advance editor mode!
If you are on the simple editor mode
Click on the button under "Table unit conversion". You will see a dropdown from which you can select the unit to convert from and to! So let's say your table measurements are all in inches; you would want to select "inches -> centimeters" options
To change the unit system, click on the purple button.
After the unit is set up, you will now see unit conversion button show up!
If you are in the Advanced editor mode:
The Table unit conversion button is still there. So, you can follow the same steps above to set units.
What is different in the advanced mode are the black arrows above each column (if the unit direction is column) or each row if the unit direction is row.
Click on the black arrow, which allows you to set the unit on a per-measurement basis when you want multiple units in the table.