trying to create a find function based on a changed cell, using VBA

Hello.

I am trying to combine 2 VBA codes and I am really struggling
the following is a code to alert me whenever a value is entered into column 1 of the worksheet, i am going to change this to only trigger when the value is changed so it does not equal zero
Capture.PNG

the next thing i want to do is add the following function that i found online to it in order to search column 3 of the worksheet for the last cell that matches this value (EG if "A1" is entered into column A, it will search for "A1" in Column 3 and select the last result

Capture1.PNG

after this i am going to add an IF function that if column 4 is blank then it will paste the information from the original row into the new row (excluding columns 1 and 3) and delete the information from the original row (excluding column 3).
if column 4 is not blank it will insert a new row afterwards and then paste all of the information into the new row (changing column 3 to the value searched for)and delete the information from the original row (excluding column 3).

Any help with this would be greatly appreciated as I am relatively new to using Visual Basic.

thanks for letting me know how to add code while keeping formatting. and thank you For all your help.