Assuming you walk at around 3 miles per hour you would cover 3 miles in 1 hour of walking time.
So to cover 874 miles you would take the 3 miles per hour and multiply that by 8 which is the amount of hours you would likely walk in a day.
So in that 8 hours of walking at 3 miles per day you would cover 24 miles in one day which is not all that much of distance but is a lot of walking.
So if you can cover 24 miles in one day of walking it would take you at least 37 days of walking to walk 874 miles.
But then again you might decide to stop and rest for a few days before continuing your walk because you'll really be tired after even 1 day of walking.
So it could take you 2 or even near 3 months to complete a 874 mile walk unless you do a lot more walking in one day to get the 874 miles of walking done sooner.