Auto fill cells depending on another cells content

Sounds like you could use a lookup function.  I would suggest creating a lookup table with meter size names and values:

name  value

U6     0.0028

E6      0.008

then in column F you use a formula like:

=XLOOKUP(E2, [name column], [value column], "n/a")

for the [name column] and the [value column] those could be cell references like Z2:Z10 or

you could 'name' those ranges like Meter_Names (if you highlight the column of cells then in the upper left the box to the left of the formula entry box you can just type the Name in there or use the Name Manager) or

you could make it a Table (use Home-> Format as Table) and then name it (click on cell in that table and then a Table menu item will show and then all the way on the left you can name that table) and then you can use Structured Names like:   MyTableName[name]