Hello,
I have found the most reliable way to convert and add system drive storage is to make the transition in stages. And enforce that only ONE instance of the operating system is present. So obliterate the Windows installation from the old drive if it will be re-installed after making the new one work, as the only drive installed.
If your system has an optical drive, that will have a SATA format connector, it is easiest to purchase SSD's that also have SATA connector. These are packaged in carriers with exact dimensional conformance to magnetic hard drives. Check your system manual for the speed of the optical connector, it is unlikely to be SATA 3.0, A mounting bracket converter is mandatory. Validate your new SSD specifications to be sure it will downclock to the SATA speed available.
For replacing the OEM magnetic hard drive, it is also simplest to select an SSD with the same mechanical format as the magnetic drive. Then simply replace the mounting brackets and replaciing the new SSD where the magnetic hard drive was is simple. 1TB or more drives will install with no issues. To find one for purchase select a reputable mfr of devices. Use their fitment database to select yours. I am in USA and use crucial.com.
Back up your user data from the old drive to separate external media. Don't bother backing up the OS files.
Download Windows 10 installation iso image from Microsoft.com Use the special software from the same webpage to write a bootable installation USB.
Validate your machine serial number is linked to your Microsoft Account. This is NOT your Lenovo account. Microsoft.com has ways to establish your microsoft account.
Install the new blank SSD.
Boot from Windows installation USB and install Windows. With the active microsoft account information, software key activation will happen seamlessly in the background. IF installation asks for the key, simply click past saying "I don't have key."
Restore your user files.
Enjoy!
Sincerely,
Usedtoberich