I'll take a day off while I'm on the business trip
I'll take a day's holiday during the business trip
I'll take a day off at the destination
「出張先で休日を取ります」= I'll take a day off while I'm on the business trip / I'll take a day's holiday during the business trip / I'll take a day off at the destination
ボキャブラリー
出張先 = (business trip) destination
休日 = day off / day's holiday
取る = take
「出張先」を直訳すると「business trip destination」になりますが、これは少し不自然な言い方です。代わりに「出張中」の「during the business trip / while I'm on the business trip」という言い方を使った方が自然です。