Windows 10: Best order to move 2 HDDs to new PC: pre or post upgrade to W10?

Hello everyone, I just build a new PC based on an ASRock X99 Extreme 4 mobo & i7-6800K. I currently have it up and running with 2 SSDs: 1- 1TB Samsung EVO 830 and 2- 500GB Samsung EVO 830. The 1TB SSD is a clone of my old PC, a Windows 7 Ultimate machine. I've had it running fine for several hours now and all seems to be working well. Frankly, I am surprised at how well the clone process worked, given that i had 450GB on my old HDD but it seems totally fine at this point.

I do want to upgrade this new PC to W10, but I still have two 2TB HDD data drives to move over from the old W7 machine. My question is, what is the best order to move those drives? Should I move them now and TEHN upgrade the entire new PC to W10? Or, should I upgrade it first, with only the 2 Samsung SSDs, and then move over the 2 HDDs after the upgrade?

I have upgraded several other PC from 7 to 10 (crypto-currency mining rigs) so I am familiar with the process, but those were bare bones with almost no extra data on the SSDs. What I am unsure of is how the immense amount of extra data is going to affect the upgrade process. I've already got 450GB on the boot SSD, and the 2 HDDs are about 75% full... so about 3TB between them. Not sure if this will hinder the conversion process or not. Any advice would be appreciated.

:)

 

Activate Windows after booting on another computer

Windows installed on your hdd was activated using the original device. You moved it to another device and it now need a new licence key.

How was the hdd activated on the original device, if it was a digital licence after the free upgrade or pre-installed by the manufacturer then it can't be moved to a new device. It is only activated on the origianl device.

 

mail app

Mail app has completely disappeared form task bar and start key

 

It won't matter either way.