This should be easy for me to do, but I'm hitting a wall as to why the following options are invalid expressions.
I have a Select action I am using, to help filter column results from a SharePoint list. Within this action, under the Map section we can add values. Looks like this...

The value I am struggling with is my Event Type value. It looks like this as an expression...
@item()?['Event_x0020_Type']
It produces something like this...
["one","two","three"]
But I want....
"one", "two", "three"
I tried adjusting this value to be an expression like so...
item()?join('Event_x0020_Type',',')
and
item()?join(outputs('Event_x0020_Type'),', ')
but neither of them are valid expressions.
Please help