I took my map card out of my lowrance 320 when i sold my boat,, my son has purchased a boat that has a Lowrance 520 on it,, i put the map card in but for some reason it just is showing the lake out,lines no way points cont lines etc.

Try going into the menu and telling the unit which card it should look for.

Not only switch over to the Navionics Card like Dayne said, but select the zone just like you had to do on the 320 you had.

Waypoints won't be on a Navionics card. They needed to be saved to a blank SD card. They are on a unit but you have to save them to a blank card to move them to a new/different unit.

Yep, their saved to the units memory, not the card.