I have an old SD card that was used with a PI3. Like a lot of people at the time i never did an update for it.I have recently got a PI 4, can i use the card in my PI 4 and update it for the firmware to boot from SSD?.Or do you have to do all that when you first put a system on the pi?If i did would i have to do rpi update then do a rpi eeprom-update or could i just do the eeprom one?Why i am asking is i have another post on here about flashing a Raspbian on a SD card i tried doing it many times, and come to the conclusion i have been sold fake SD cards on Ebay.As i bought them some time ago i can,t get a refund.I think i have the answer it was Noobs pre loaded card ,I have looked on other posts on here and they say you cant get SSD boot with it.I have flashed Raspdian on the pi3 SD all done in ten minutes.
First of all, a Raspberry Pi 4B is only supported by the Raspberry Pi OS based on Buster. This is an important showstopper for just updating an old Raspbian version. In addition the Foundation does not recommend to upgrade an old version to a new one. At Updating and upgrading Raspberry Pi OS you will find:
Warning: Upgrading an existing Stretch image is possible, but is not guaranteed to work in every circumstance and we do not recommend it. If you do wish to try upgrading a Stretch image to Buster, we strongly suggest making a backup first — we can accept no responsibility for loss of data from a failed update.
I strongly recommend to setup the operating system from scratch for your new Raspberry Pi 4B. If you try an upgrade, please don't ask here why it doesn't work. I wish you good luck then ;-)