Another way you could do is just start a new project in a different folder and run the project setup and set the sample rate to 48k and then import the 44.1k tracks and you will be asked if you want to convert them.
Another way you could do is just start a new project in a different folder and run the project setup and set the sample rate to 48k and then import the 44.1k tracks and you will be asked if you want to convert them.