Yap.Town

の予約をしたいのですが

I'd like to make a reservation for…

→ の
phrase Rare #39,053
I'd like to make a reservation for… Attach の to the thing you want to reserve. The ending のですが makes the request sound polite and indirect.
JA: 来週の予約をしたいのですが。
EN: I'd like to make a reservation for next week.

今晩の予約をしたいのですが。

I'd like to make a reservation for tonight.

キング先生の診察の予約をしたいのですが。

I’d like to make an appointment to see Dr. King.

診察の予約をしたいのですが。

I'd like to make an appointment to see a doctor.

洗髪とセットの予約をしたいのですが。

I'd like to book an appointment for a shampoo and styling.