How to install New internal Unformatted HD on 2010 Mac Pro

[Chris L]

I have a 2010 (5.1) Mac Pro and the Macintosh HD failed and I have a new Toshiba x300 HD that is unformatted that I would like to install and use as my scratch disk. When I have the new HD in slot 1 and no other HD’s installed I turn the computer on and only get the grey screen. If I turn on the Mac Pro with the new HD installed while holding Command R I get the folder with question mark error message. How should I proceed?

Once I format the HD I have the High Sierra OS on a Lacie external drive that I am hoping I can use to load the OS onto the new HD on my Mac Pro.

[kers]

I have a 2010 (5.1) Mac Pro and the Macintosh HD failed and I have a new Toshiba x300 HD that is unformatted that I would like to install and use as my scratch disk. When I have the new HD in slot 1 and no other HD’s installed I turn the computer on and only get the grey screen. If I turn on the Mac Pro with the new HD installed while holding Command R I get the folder with question mark error message. How should I proceed?

Once I format the HD I have the High Sierra OS on a Lacie external drive that I am hoping I can use to load the OS onto the new HD on my Mac Pro.

Did you make a backup - with Timemachine?
It is invented for exactly that reason.
If you have and it is on a USB drive - you connect it and turn on your computer with the empty harddrive.
It will start up from the USB-drive. From there you reinstall your old computer.

If you do not have a time machine backup on a different drive you have new hardware but no software.
you need somebody with a mac to format the new Harddrive and reinstall the system probably from again some USB drive.
(Do you say you lost all your data? )

[Chris L]

I found this support to create a USB flash drive bootable installer and in the middle of process now.( https://support.apple.com/en-us/HT201372 ). Seems like it will work but i will let u know. i do not use time machine. i did not lose data because it was all backed up an an external HD.

[BobShaw]

i do not use time machine. i did not lose data because it was all backed up an an external HD.

Well maybe you have not lost data but you may have lost the OS, the Applications, users, printers, passwords and settings, plus you have a lot of extra work.
Time machine is brilliant and you would be up and running with an exact same machine in about 4 hours.