How do I obtain record of Employee Stock Purchase and Restricted Stock Units (RSU)?

My last employer had an employee stock purchase plan (ESPP) and a part of the compensation package also include restricted stock units (RSU). I left that employer over a year ago. I had held onto ESPP and RSU shares, which were transferred to a new brokerage. When I was an employee, there was an internal website to lookup items such as Total Share Vested\Released, Shares Withheld (Traded) to Pay Taxes, Date Vested\Release, Market Price on Vesting Date (per share), Price You Paid per Share (if RSU, than 0), and Purchase Commissions or Fees Paid. Those data fields are being requested by TurboTax for shares that I sold in 2020 yet obtained over 3 years ago.

Any guidance on how to obtain the historical information?

I do have an inquiry to my employer's HR department. As a little more context, the brokerage firm used was changed 2 or 3 times while I was employed, and as mentioned the shares were transferred by me to a different brokerage firm after I left the company.