Solved adding hard drive

I installed FreeBSD 11.1 on my HPC and I had disconnected the sata 3 port of the western digital disc N ° 1 of 3 tera bytes, so I installed the FreeBSD on the disk N°2 of 2 tera bytes in multi partition in the following order: NetBSD, OpenBSD and FreeBSD 600 gigabytes each,the boot manager is the grub of Debian 9.1, which allows me to choose the operating system has started.
When I reconnected the disk # 1, from the BIOS I chose which disk I want to use.
Now I choose the disk # 2 and run FreeBSD, and I have an error on the FreeBSD that stops at mountroot>
It tells me that I started from /dev/ada0s3a, I do not have access to the /etc/fstab file, what should I do?

Your disk containing FreeBSD has become ada1 after you connected the other disk. At the bootprompt ufs:/dev/ada1s3a should work.
how to edit the /etc/fstab file
Any editor works, but you need to be root. Look at the other entries for guidance, and there's a man entry. BTW, you don't need to add spaces in file names in this forum. :)
philo_neo please stop putting spaces where they don't belong, there's a difference between /usr/ports and / usr / ports /. The first is correct, the second is a syntax error.