The plural would be a normal S plural, twos. As a numeral, 2s is recommended, but the generally frowned-upon apostrophe version (2's) is sometimes clearer.
The plural way to spell studio is studios.
The plural is resources.
The plural is cantaloupes.
The plural is hooves.
The plural is cherries.
The plural is roses.
The plural is "emeralds."
The plural is bridges.
The plural is "recesses".
The plural of "roar" is "roars".
The plural of "frill" is "frills".
The plural is lullabies.