The Bible does not include the specific length of time that Job suffered. However, multiple verses indicate that the suffering took place over at least a few months.
The Bible says Job experienced many trials, such as the killing of his livestock, severe illness, and the death of his three daughters and seven sons in a storm that was probably a tornado. Job 2:13 explains that Job's friends sat with him in silence for a week after noticing he was grieving because of the trials, which implies the trials lasted at least that long. Also, Job 7:3 references months of hardship.