press c at the first box
then ls to check your partitions/disks
Then indicate which vmlinuz and imitrd.img you want to boot with.

grub> set root=(lvm/mint--vg-root)
grub> linux /boot/vmlinuz-4.4.0-112-generic root=/dev/mapper/mint--vg-root
grub> initrd (hd0,msdos1)/boot/initrd.img-4.4.0-112-generic
grub> boot