Estoy en el tercero grado
(I am in the 3rd grade)
Three in Spanish is "tres".
You could say "el quinto grado".
It depends on what you mean by "grade" If you are referring to quality, such as "what grade is this cut of meat?" or "I don't care what grade you buy as long as it does the job." The Spanish for "what grade" is "Qué grado?" If you are referring to an academic grade describing how many points you have on an exam or similar, the Spanish for "what grade" would be "Cuál nota?"
el cuarto grado
You can say "Ella era en el sexto grado."
estoy enfadado/enfadada (girl)
estoy en el grado 5
"three dollars" in spanish is: "tres dolares" three - tres dollars - dolares
Tres
tres canciones
tre patas
Tres hermanas.