1
My job is a nurse.
I am a nurse.
I work as a nurse.
We can ask What’s your job?, but we answer I’m a… or I work as a…: ‘I’m a teacher.’ ‘I work as a teacher.’
2
Most people have a computer in their job.
Most people have a computer at work.
Use to/at/from work, not job, when you mean the place where someone works: ‘I go to work at eight.’ ‘She’s at work.’ ‘He has just come home from work.’
We can use in my/your/his/her job to talk about the activities or skills that a job involves: ‘I use English in my job.’