Mounting and using new volume with nextcloud installation

Hi there,
I have a Nexcloud installation with snap on a Ubuntu 20.04 Virtual Machine. I have terminated the available storage of the VM, however my provider gives to me the availability to buy external volumes and attacch them to my VPS. I attached the volum to the VPS and it is correctly mounted. Now I would like to enlarge the Nexcloud partition with the memory from this memory.

Nextcloud is on sda1 partition, new volume is on sdb partition.

Do you have any suggestion to complete the job? Or any suggested tutorial that I can follow step by step?

Thanks guys