Attempt to index local "player" a number value?

Problem

You're changing the Player variable in the event to a number value. MouseButton1Click does not return the player who clicked on the button. Since MouseButton1Click is used in Guis often times held in PlayerGui it is completely unnecessary for you to get a player variable in the event. Instead the event will provide the location of the mouse in the button at the time of the click.

Solution

Just remove the Player variable in the event. It is not necessary unless you want to do like animations, then I would just recommend renaming the variable to something else.

Final Script

local Player = game:GetService("Players").LocalPlayer

function yes()
    Player.leaderstats.WantedLevel.Value = Player.leaderstats.WantedLevel.Value + 1
    Player.Character.Rank.Frame.Name1.Text.Value= Player.Name.."- Robbing"
    local h = script.Parent.Parent
    h.Visible = false
    script.Parent.Parent.Parent.OneThousand.Visible = true
    local rob = script.Parent.Parent.Parent.RobbingPresent
    rob.Script.Disabled = false
    end
end

script.Parent.MouseButton1Down:connect(yes)

Just a heads up, this script is not FilteringEnabled compatible, so if you plan on using a similar script in a FilteringEnabled environment you will need to revamp the script.

Hopefully this answered your question, if so do not forget to hit the accept answer button. If you have any questions, feel free to comment below.

The problem is you are trying to access your local variable Player. However the 'Player' argument of your yes() function shadows it, which means your function cannot see your variable Player because the argument has the same name.

Now, for the reason the script errors "attempt to index a number value". The thing is the MouseButton1Down event passes two numbers as arguments to your yes function callback: the x and y coordinates of the click. So your Playerparameter gets assigned the 'x' coordinate and the 'y' coordinate is lost (because your function declaration does not specify enough arguments).

Remove "Player" from the list of arguments to yes and everything should be alright.