Bad magic number in super-block

dumpe2fs is specific to the ext2/ext3/ext4 family of file systems, so if you use something else, then that would complain in exactly the way described that this is not an Extended file system.

If it is one of the ext family, then running fsck will clean this up nicely, as ext stores multiple copies of the superblock in different spots of the disk, and fsck would just use another one and restore the one in the beginning.

If it is a different file system, fsck still has a good chance of working, although a lot of the newer file systems are not that resilient anymore.

Last but not least, check that the device names are the same when booting from a live stick -- it is quite likely that the USB stick as the boot device is now the first one found, so it is named sda, and the harddisk is now named sdb. Use fdisk to look at the partition table, whether it matches what you expect, especially the size of the disk and the partitions.