Needing help setting up Nano Electronic Lock with Keypad 3x4 with interruptions

Hello, I'm working on a project in building an electronic lock with an Arduino Nano by using a 3x4 matrix keypad, using interruptions. In the project, is to achieve a user interface that will store "10" passwords for the ten users. The program will check the users inputted 4-digit password with the "10" stored passwords that were in the 2-D Array as shown below. This will be displayed on a 20x4 LCD display, connected to the Arduino Nano board. NO libraries to be used.

HELP NEEDED: If I can receive help on setting up the interruptions with the Arduino Nano to the
requirements below, I would greatly appreciate all your efforts. Store and values of the
keys that was pressed then checks it with the 2-D array, and if it works, then proceeds, if
not, check again.

Interruptions used for 3x4 Keypad:

OUTPUTS: to Keypad("Row"'s of the Keypad)
-PB5 (Top Row (#1-3))
-PB4 (2nd Row (#4-6))
-PB3 (Goes to a buzzer)
-PB2 (3rd Row (#7-9))
-PB0 (4th Row (#*-#))
-PC5 (Goes to Relay to Actuator for door lock)

INPUTS: to Arduino("Column"'s of the Keypad)
-PC2 (Left Column)
-PC1 (Middle Column)
-PC0 (Right Column)

Internal Pull-up Resistors:

-PORTC |= 0b00000111; //Intialize PULL-UP RESISTORS

/***********************************************/
//2-D Array storing the 10 user's passwords

char cUsers[10][8] = { {'2','7','3','5'}, //Users Passwords
{'9','9','3','8'},
{'5','5','0','0'},
{'0','0','7','4'},
{'4','5','9','6'},
{'1','3','8','7'},
{'0','9','1','1'},
{'2','0','1','0'},
{'2','0','1','6'},
{'8','9','2','3'}
};

char cData[15]; //Array to store the pressed keys and check the passwords stored in cUsers array.

Thank you so much!