Hi and welcome .What model Volvo do you have? Do you hear the engine doing anything?
turn on your head lights if they look bright then battery is probably ok.If the battery is ok then you may have an alarm problem or starter problem. If it is the alarm the relay is above brake pedal( large red one that says ant-theft on it) try unplugging it and plug back in. If it is the starter you can have someone try to start the car while you check for power at the small terminal on the starter.