Hi Gia--welcome!
Most foot pedals for digital dictation plug into the computer using a USB port. Most transcribing machine pedals that I know of do not have a USB configuration so I think you are going to have to buy a new foot pedal. If you don't want to buy brand new, try Ebay and see if they have any--maybe search for USB transcription foot pedal. Otherwise
Medword.com (this site) has digital foot pedals available to purchase.
If you have a regular headset (i.e., not a Dictaphone headset) with a connection used for CD players and such you should be able to use that. USB headsets are also available, but as long as you don't have a Dictaphone headset you should be okay.
Hope that helps!
Double check to make sure what types of ports you have before you buy!