Windows 11 (Update)
I have been running the Windows 11 beta and pre-release built for several weeks. Since then, Windows 11 has finally been release. Unfortunately, it is not available as an update for my old laptop. It is so old that the support personnel from AfterShockPC told me it is end of support when I asked about buying a replacement battery.
Installing the Released version of Windows 11
With the power of the internet, I found a way to install the Released version of Windows 11. The author of this article has a computer very similar to mine; i.e. an old gaming rig that still works well.

Followed the instructions given, my laptop was updated. Easy.
Missing Microsoft Store (FIXED)
Joy was cut short when I realized Microsoft store was not found anywhere on the device. After some effort searching the internet, Method 3 on this website solved it for me. Before trying the method, I checked that the file in the link is not a malware. As it come from Microsoft, I proceeded with successful outcome.

Just in case, the information or website page goes missing. I copied the details here.
Method 3: Repair the Windows Store Manually
If you still cannot fix the Microsoft Store missing Windows 10 error, then you need to repair the Windows Store manually. Follow the instructions below step by step to run this method.
Step 1: Download the ZIP file from this link. Unzip this file and paste it to your desktop. To be more specific, copy and paste the file in C:\Users\Your_Username\Desktop.
Note: You need to replace Your_Username with your actual account username.
Step 2: Press the Win + X keys at the same time to choose Windows PowerShell (Admin). Click Yes to open Windows PowerShell as an administrator.
Step 3: Type Set-ExecutionPolicy Unrestricted in the window and press Enter.
Step 4: Press Y and Enter if the program asks you to change the execution policy.
Step 5: Type cd C:\Users\Your_Username\Desktop.\reinstall-preinstalledApps.ps1 *Microsoft.WindowsStore* in the window and then press Enter. (You need to change Your_Username to your actual username.)

Step 6: Minimize Windows PowerShell. Open the Run box and then type wsreset.exe in the box. Click OK to reset Windows Store cache.
Step 7: Type Set-ExecutionPolicy AllSigned in the Windows PowerShell window and then press Enter.
Step 8: Restart your computer to make the changes to take effect. Then check if the Windows 10 Store missing error still persists.