Simplify the following text for a Grade 8 native English-speaking person.
Original: Shortly afterwards , in 1981 , Dickinson was hired as Iron Maiden 's new vocalist , replacing Paul Di ` Anno , and debuting for that band with the 1982 album The Number of the Beast .
Simplified: Later that year , after Paul Di ` Anno left Iron Maiden , Dickinson was chosen to be the band 's new singer .