Formatting collected data in a cell

Sorry about this basic question, but for some reason the search function on the website does not appear to be working.

I have the following in cell formula

="The design flow rate that must be produced is "&ROUND(Overview!E15,0)&" m3/day net of UF cleaning."

the data is being collected correctly, however I cannot collect the data in the right format, i.e. the cell looks like this:

The design flow rate that must be produced is 235000 m3/day net of UF cleaning.

The "235000" is the data coming from the other sheet, however I would like to use commas, i.e. "235,000"

I do not seem to be able to do this no matter what format I change the destination cell or the data from the collected cell?

thanks in anticipation

THANKS FOR THE REALLY QUICK RESPONSES