The England vice-captain will move one place up the order for the four-Test challenge, with Pakistan in England for the first time since the controversial 2010 tour.
Root hailed coach Trevor Bayliss and captain Alastair Cook for floating his proposed promotion early on in order to let him steal a march in his own mind.
“We had a few discussions throughout the season that it could be a possibility moving forward,” said Root of talks with England’s management about moving to number three.
“I think the fact I had quite a long time to think about it and to chat it over with the selectors and Trevor and Cooky it probably made it a bit easier, rather than being thrown into the role.
“The way they’ve dealt with it has been really good and it’s given me time to get my head around it.
“I feel pretty comfortable going into the series and it’s now just about trying to make sure that moving forward that’s something I feel comfortable with and I can keep making big scores and contributing to winning Test matches.”
England host Pakistan at Lord’s first up, with the first Test starting on Thursday, where Mohammad Amir will make his return after his ban for spot-fixing.
Root rejected suggestions England’s middle order will be weakened by his move to No 3 and Ben Stokes’s injury absence.
“I think that’s probably harsh,” said Root when asked if England’s middle order is a work in progress.
“Someone like Jonny Bairstow would consider himself a middle order batsman, and he’s taken his game to another level.
“This series here now is a great opportunity for guys to stand up and really put some strong performances in.
“Guys like James Vince who will really be looking forward to getting back out playing red-ball cricket again.
“He’s got a little bit of experience under his belt and will gain confidence from that.”