As result of changing your hardware, Bitlocker is requesting the Recovery Key, since it cannot distinguish legal operation from possible attack. This is done in order to protect your data.
In some cases your BitLocker recovery key is automatically saved to your Microsoft Account. So, look there for this key.
In other cases, when the Bitlocker is activated by Administrator, through the Windows Settings or trough the Control Panel, user is asked where to save this key. The possibility may be: Microsoft Account, USB memory stick or printout.
In case that you can't find the Recovery Key, you will need to boot from Windows Installation USB and reset your Windows (loosing all your data).