This article explains why you cannot update a Windows 10 LTSC image to Windows 10 Pro and an outlines alternative solution.

The Windows 10 LTSC image provided by Elo comes with an OEM Enterprise edition embedded with the LTSC-specific OEM license key. Due to licensing restrictions, it is not possible to upgrade or convert an LTSC image to a Windows 10 Pro image. Microsoft's licensing terms strictly prohibit this conversion, and attempting to do so will not succeed.
 

Elo does not offer Windows 10 Pro licenses.
 

If a Windows 10 Pro image is required, it must be purchased separately from Microsoft, along with its own license key. Installing a Windows 10 Pro image will overwrite the factory-installed Elo image, which includes all pre-installed system and board drivers. Therefore, after installation, you will need to manually reinstall the necessary Elo drivers to ensure proper functionality.