Regardless of gender, the word is the same as in English.
You should say shorts
Shorts is a mass noun. Because of that you use the quantifiers: a pair of
, and so on...
Eu pus um short = I put on some shorts
. / I put on a pair of shorts
Você tem shorts (masculino)? = Do you have shorts (for boys / for men)?
Este shorts (feminino) rasga à toa = This pair of (girls') shorts
There are some interesting articles about clothes (1) and mass nouns (2) on English Experts site:
Note: The term short trousers
is used to describe trousers reaching only to the knee, as worn typically by young boys.
I hope I've helped you.
(1) Pearson Education. Longman Dictionary.
(2) Oxford Dictionary.
(3) LEFLER, Anna. From A-line to Z-snap, the words every woman should know
. Adams Media.