Welcome to the community!
I assume you upgraded your phone. If the new phone uses the same sized SIM card, you can simply remove the SIM from your old phone and place it for use in your new phone. You'll then be able to use your new phone with the same number and services as with your old phone.
On the other hand, if your new phone uses a different sized SIM card, you might need to get a new SIM card. Depending on your actual card, some of them are the 3-in-1 type cards. That is, their size can be adjusted by removing or replacing pieces (see image here). If your new phone uses a smaller SIM than your old phone, you might be able to remove the corresponding parts. If, however, your SIM is only one-size, you'll then have to get a new SIM. You can get one from a Fido store or contact customer service to have one sent to you. Alternatively, you might consider sending @FidoSolutions a PM. Once they verify some information, they'll also be able to access your account.
If you do get a new SIM, you'll need to update the SIM card information on your file. You can do so via My Account --> Usage & Services --> Mobile --> Quick Actions (near bottom of page) --> Update SIM card. You'll be required to enter your old SIM number as well as your new SIM number. You should note that once your card is updated, your old SIM will be deactivated.
Hope this helps 😀