View the link below.
http://www.discountedwheelwarehouse.com/Mercury___Vehicle_Bolt_Pattern_Reference.cfm
Same year Mystique and Contour
Unfortunately the lug pattern is different, the wheels will not interchange. You can use Thunderbird or Cougar wheels.
5 lug by 5inches
5x4.75
I'm assuming it is the same as the ( 1996 ) model year of Mercury Cougar : ( there are 5 lug nuts for each wheel / total of 20 )
It has a 5 on 4.5 bolt pattern.
5x5.5
4 x 4.5"
4
5x4.75 or 5x4 3/4 standard GM.