mounting harddrive on ubuntu gives error?

I am trying to perform a simple task (to the native ubuntu user, but not to me :D): mounting an external harddrive on my rasperry pi, in order to copy some data onto it, then connecting it back to my windows pc and transfer the data.

I identified the harddrive by sudo fdisk -l:

Disk /dev/sda: 931.48 GiB, 1000170586112 bytes, 1953458176 sectorsDisk model: Elements 25A2Units: sectors of 1 * 512 = 512 bytesSector size (logical/physical): 512 bytes / 512 bytesI/O size (minimum/optimal): 512 bytes / 512 bytesDisklabel type: gpt

I followed some steps that I found online:

• mkdir mnt_sda
• sudo mount /dev/sda mnt_sda/

The latter gives me the following error:

mount: /home/user/mnt_sda: wrong fs type, bad option, bad superblock on /dev/sda, missing codepage or helper program, or other error.

I also read something about having to create a new linux-compatible partition on the drive first, but it seems the disk needs to be completely reformatted for this and the existing data will be lost. Any way to circumvent this?

Thanks!