Continue printing after power off and power the 3D Printer on again (no replies)

I want to add that feature (detailed in the title) in my 3D Printer but I don't know where to write the code and how to write some parts of the code.
That is how it must work .....
When the printer is working :
1- It have to save the auto bed calibration values, the temperature and the number of the current line of the G-code in text file in the SD card with the same name of the current object.
2- When it finishes printing the text file must be deleted.
3- Every time I power the Printer ON it must search if there are text file in the SD card.
4- If there is no text file in the SD card The printer starts normally.
5- If there is a text file compare it's name with the G-code files.
6- If there is no G-code with the same name in the SD card The printer starts normally.
7- If there are a G-code with the same name ask the user if he wants to continue printing or not.
8- If YES, heat up the nozzle then raise the Z axis 6 mm, home X axis, Y axis, heat up the bed and continue from the line saved in the text file after moving the Z axis 6 mm down.
Looking forward for your help.
Regards,,