SOLVED Upgrade iMac mod 14,1

[Jaygon]

I have an original 21.5" iMac (late 2013) Model 14,1 running Catalina 10.15.7 and want to speed it up somewhat. Today I bought new a Samsung T7 500 gb to run the MacOS, intending to use the much slower original 1TB HD for data and backup. My existing HD and 2 external HDs (both 500gb and run from the standard USB 3 connections), are all formatted as APFS. I tried to format the new T7 as APFS but Disk Utility would not give me an option to do so. I was advised to select MacOS Extended (Journaled) and try again. A little success in that the T7 was reformatted from Exfat to MacOS Extended (Journaled) and the T7 is recognised by the iMac and can be read... but, I cannot format it as APFS. If you can help me, some successful advice would be gratefully received.

 

[Lufbrarunner]

When you formatted as 'MacOS Extended (Journaled)' did you set the scheme as 'GUID Partition Map'?

 

[Jaygon]

Hi Lufbrorunner, Thanks for your very fast response. Yes, it does sound quite funny and the answer is, no I didn't. I did do more reading and watching of utubes etc, but much of what I saw did not seem to this extended-age retiree to make much sense, so I did more researching last night. I should have waited a bit longer and I would have then read your very politely and gently hinted response. Yes, I had to redo that, change the format to APFS and set the scheme to 'GUID Partition Map'.
However, of course I still need to inform my now appropriately formatted (and oh so fast and readable external SSD) that my apps are all still located on the old internal HDD along with all their preferences and other requisite data. Duh. That, this old fart completely forgot and his temperature rose further. Sob.I will keep looking for the fix there but in the mantime thank you again and I will mark the thread as solved.
Cheers.