Execution plan doesn't show memory grant
Memory is granted at runtime, so the information you are looking for can only be seen in a post-execution (a.k.a "actual") execution plan, not a pre-execution ("estimated") plan.

If you are using SQL Server Management Studio as a client, CTRL-L is mapped by default to show an estimated execution plan. You can turn on post-execution plans using CTRL-M.

The tooltip on the root node of the plan only gives very limited information. For more detail, open the Properties window and look at the memory grant information there when selecting the root node of the "actual" execution plan.