I don't really know what ProtectRouteProps is and what I should put in it.

There are no props. This is clear by the usage:

<Route path='/createItem' element={<ProtectRoute />} />

No props are passed to ProtectRoute. You can drop the props object:

import { Navigate, Outlet } from "react-router";
import { RootStateOrAny, useSelector } from "react-redux";

export default function ProtectRoute() {
  const userSignin = useSelector((state: RootStateOrAny) => state.userSignin);
  const { userInfo } = userSignin;

  return userInfo?.user?.isAdmin ? <Outlet /> : <Navigate to='/' replace />;
}

The problem now is that can't access CreateItem because is going on the ProtectRoute page that is an empty one. What should i do?

"Auth" routes are what are called layout routes. They apply some logic, perhaps some styled layout CSS, and render an Outlet for nested Route components to be rendered into. The nested Route components use the path prop for route matching.

Example:

<Route element={<ProtectRoute />}>
  <Route path='/createItem' element={<CreateItem />} />
  ... other protected routes ...
</Route>

 <Route exact path='/Login' element={<Login name="Login Page"></Login>}></Route>
    <Route element={<Protected/>}> 
    <Route exact path='/' element={<Home/> }></Route>
    <Route exact path='/Content' element={<Content />}></Route>
    </Route>

   <Route path='*' element={<Login/>} ></Route>
  </Routes>

Create Protected.js

import { Navigate, Outlet } from 'react-router-dom';

   const useAuth = ()=>{
    if(localStorage.getItem("isLogged")){
    const user = {loggedIN :true};
    return user && user.loggedIN
    }else{
    const user = {loggedIN :false};
    return user && user.loggedIN
   }

 }

 const Protected = () => {
 const isAuth = useAuth();
 return isAuth ? <Outlet/>:<Navigate to={"/login"}/>
 }

export default Protected