File Systems chaos after upgrading to omv4

Hi...yesterday I upgraded ovm from erasmus to version 4...I am using a Raspberry Pi 3 B+ and also a Western Digital sata drive for system files (I think) anyway...it worked fine until I copied the files to the hard drive. I also use a dual dock where there are two Seagate 3Gb hard drives...one is for data and the other a backup. I use the OMV exclusively as a Plex Media server. After a reboot the hard drives are displayed correctly in "Disks"...but files systems show the first 3Gb hard drive as being 228 Gb of which 4.9Gb are used. The second hard drive throws an error when I try to mount it. I have a 30+ year collection of Movies, Sports, etc on the 3Gb sda1 and backed up on sdb1. The sda1 is mounted but not referenced...the sdb1 will not mount. I do not know what to do to repair this or if my collection is destroyed. I need help from someone whose knowledge level exceeds mine to give me advice...if possible. Thanking you in advance! Oh...movies won't open in Plex with a message to check to see if file exists. I have re-scanned library files and they are all there but, as I said throw the error, When I refresh meta data some are sill there a lot are blank placeholders even though they have the file name underneath. I sincerely appreciate anyone's assistance...and do hope I can recover these files. thanks again.