This issue can be caused by two issues. If the keys I-O-P-[-K-L-;-,-.-/ are displaying numbers, please press the NUM LOCK button on the right side of the keyboard.
If using the shift + 1 / shift + 2 / shift + 3 etc is not showing the correct characters, you will need to set your keyboard language, as most likely it has been changed and does not match up with the keyboard you currently have. Below are instructions on how to do this.
Go to the bottom left search bar and type "Control Panel". Press Enter.
Select Region & Language, then Keyboards & Languages (tab).
Click "Change Keyboards". Select a region such as United States or Canada to resolve this issue.