hello Prajwal at least you got the grub command !
There are probably 2 approaches:
1) Put one of the grub rescue programs onto a usb (or cd if you have cd drive)and boot up
2) Use the grub command line and manually tell it where to find your inital ramdisk and image.Its a bit of work and learning curve but not that bad.
If you want to start with 2)
Start with that and see if you get anything; paste us what you get. from there ..we can continue
A generalised process i noted on my shystem was something like this:
(hd0) (hd0,msdos2) (hd0,msdos1)
If you’re running GPT it will say (hd0,gpt1).
grub> ls (hd0,1)/
lost+found/ bin/ boot/ cdrom/ dev/ etc/ home/ lib/
lib64/ media/ mnt/ opt/ proc/ root/ run/ sbin/
srv/ sys/ tmp/ usr/ var/ vmlinuz vmlinuz.old
So grub uses a slightly different naming system normally you might see /dev/sda1 , /dev/sda2
if you see something like (hd0,gpt1). from memory hd0 means first drive and gpt shows you have the new style gpt partition.
IN the above when i looked into (hd0,1) vmlinuz and initrd.img where found . Thsts alog the lines you will be looking for. If and when you find them , grub is then told to use them and get manjaro booted