Er I don't think you'll find that conservative synagogues do saturday weddings.
Obviously you will know some of the crowd and you have your own taste.
I don't know how conservative you mean but IME
Probably not pants but some congragations it's ok.
Mid-long legnth dress/skirt and jacket.
Hat (married women (or in some congragations over 21 KWIM) have to cover their head).
Covered arms (ie long sleeves) and feet (usually not strappy sandals)
Nice handbag
Not all black or white
I hope this helps but of course I am European so maybe things are different where you are.
Have a wonderful time whatever you decide to wear.