From this post
Unity Technologies:
For 2019.2 and above, if you created a new Unity project, you will need to add the
2D Tilemap Editor
package from the UnityPackage Manager
(under Window → Package Manager) to your project to be able to create Tiles and access theTile Palette
.If you created a new Unity project with the 2D template, the package will be added for you automatically.
If you upgraded from a previous Unity version, the package will be automatically added as well.
For installing a package follow the Installing packages from the registry - Manuall which in short goes:
Open the Package Manager Window via Window → Package Manager
set the Filter to All Packages
search for the Tilemap 2D Editor Package
Hit Install
After doing this the options you are looking for should be under Window
→ 2D
→ Tile Palette
and Create
→ 2D Object
→ TileMap