Want to Install Windows 10 onto MacBookPro (15", Early 2011) running Sierra 10.12.6
In 2011, Windows was still being installed to BIOS boot on Macs. The drivers provided by Apple assume you will be installing for a BIOS booting Windows. You can not directly install a BIOS booting Windows on any model Mac using a flash drive. The easiest solution would be to burn a Windows 10 iso file to a DVD-R DL.

Creating a burnable iso image from Windows 10 USB flash drive installer.

According to the instructions provided by Apple, you are suppose to download the ISO from Microsoft. Read Step 2 in the document I have linked to. 

However, you may be able to burn the ISO file from the USB flash drive Windows 10 installer you purchased to the DVD by using the command given below.

Using a machine running Windows 10, I created a Windows 10 USB flash drive installer. After inserting the flash drive in a 2011 iMac running High Sierra, I was able to enter the following command to create a bootable Windows 10 ISO file. You will need to burn the image stored in the windows10.iso file to a DVD. The image was only 4.15 GB in size so I was able to use a DVD-RW.

hdiutil makehybrid -o windows10.iso /Volumes/ESD-USB -no-emul-boot -boot-load-size 8 -eltorito-boot /Volumes/ESD-USB/boot/etfsboot.com


The name of the flash drive shown in the finder was ESD-USB. The -boot-load-size was set to 8 sectors, because the size of the etfsboot.com file was 4096 bytes and the sector size is 512 bytes. ( 8 * 512 = 4096 )

To boot from the DVD, do the following.


Insert the DVD
Restart 
Immediately hold down the option key until the Startup Manager icons appears.
Select the DVD icon labeled Windows.