You're not required to make a withdrawal the year you convert your account, however moving forward into the next calendar year, and for all future calendar years, there will be a minimum amount you must withdraw each year. The minimum amount is based on the previous year-end value of the account, and multiplied by a factor value that is determined by the government based on your age each year! If by year-end you have not withdrawn at least the minimum amount, your RRIF, Spousal RRIF, or LIF provider will automatically send you the necessary amount.
If you withdraw any funds that are above the minimum as described above, you'll be subject to a withholding tax rate. Please note that for RRIFs there is no maximum on how much you can withdraw (so long as you're okay with the withholding tax rate you'll be subject to), but there is a maximum for LIFs! You'll be prevented from withdrawing above this maximum for a LIF.
Mercer Invest Wise also offers an RRSP contribution tracker, which will allow you to estimate your contribution room with some accuracy, but we still highly recommend setting up a MyCRA profile to verify our estimation! You can follow the instructions on how to set up your RRSP contribution tracker in our FAQ article here!