lotto 'style' random number generator with duplicate checking in C#

[Mykghoul]

My first app in 30 years ... how logically bad is it?
Lame lotto number generator but found it interesting enough to motivate me to code again ... lol. I would think there is a better way to check for duplicates and an easier way to display each 'ball' number into a different label. Thanks to any who might spend a moment to look this over

            // Initialize variable to point to each number in the array
            int m = 0;
 
            // Loop until 5 random numbers have been generated and assigned to the array
            for (int i = 0; i < mmar.Length; i++)
            {
                // create arrays to utilize higher probablistic ranges for each ball
                int[] y = new int[5] { 1, 3, 8, 18, 30 };
                int[] z = new int[5] { 21, 31, 52, 63, 71 };
                // use the for loop's initialized variable to change random range
                mmnum = mmball.Next(y[i], z[i]);
                // Loop to ensure each number is unique
                for (int j = 0; j < mmar.Length; j++)
                {
                    // check the number of ball for duplicates
                    if(mmnum == mmar[j])
                    {
                        // if not unique create new ball
                        mmnum = mmball.Next(1, 71);
                        // re-initialize to ensure new ball number is unique
                        j = 0;
                    }
                }
                // put the ball number into our array
                mmar[m] = mmnum;
                // change to new array slot
                m++;
            }
 
            // Sort the numbers in the array before displaying them
            Array.Sort(mmar);
            // OLD ... START Place lotto numbers on screen
            num1mm.Text = mmar[0].ToString();
            num2mm.Text = mmar[1].ToString();
            num3mm.Text = mmar[2].ToString();
            num4mm.Text = mmar[3].ToString();
            num5mm.Text = mmar[4].ToString();