Cloning hdd to ssd

I have a system with
ssd sda → manjaro
hdd sdb ubuntu
I have bought a new ssd and with Timeshift I will transfer the contents of sdb /.
For failure reasons of sda i have to install grub on the new ssd and to start from the second (new) ssd as it does now .
The grub installation command is

# grub-install --target = i386-pc / dev / sdX?

And that’s it?

That depends - is your system a BIOS system - as in NOT UEFI

I forgot to mention that it is bios

Then it seems valid - albeit replace the sdX with the actual device (and no partition number only device) - and change your primary disk in BIOS to point to the new disk.

The primary disk now is sda and it also displays ubuntu.
If I make sdb the primary one I will have to make grub as well to display manjaro.
I have to make grub from the ubuntu disk so that Manjaro is displayed.
I’ve got this !
Thank you !