Your WiFi signal comes from your wireless router or access point. Or is your Motorola modem actually a gateway? We need specific model numbers here, but in general, to get the password is usually impossible, although you can change it to a known value if you can log in the the access point's admin interface. If you no longer have that ability, then you're usually left with resetting the access point to factory defaults and then reconfiguring it from scratch.
It's important to save your wireless settings (especially the wireless password) someplace safe so you can recover it if you forget it. The password is meant to be secure, so there are few if any opportunities to retrieve it. Some access point interfaces will allow you to make the passphrase visible, but that option is pretty rare.