switch between two y-axis columns

Here is how I have done it previously:

I create a table "Unit Type" with one column "Type" and 2 values:

Volume

Energy

I then create a measure on that table

MType = SELECTEDVALUE('Unit Type'[Type])

'Unit Type'[Type] will populate your slicer.

On the fact table, I create a measure that switches between calculations based on the value selected in the slicer

Total Volume = 
SWITCH (
    [MType],
    "Energy", CALCULATE (
        SUM ( FG[Volume] ),
        UoM[Unit of Measure] = "MMBTU"
    ),
    "Volume", CALCULATE (
        SUM ( FG[Volume] ),
        UoM[Unit of Measure] = "MSCF"
    )
)

SWITCH() is a multi-part IF statement. See this link SWITCH() for more information.

If you're still having trouble, see this link to give the community all of the necessary information:

https://community.powerbi.com/t5/Community-Blog/How-to-Get-Your-Question-Answered-Quickly/ba-p/38490

David