After City's 1-1 draw with the much-fancied Wigan Athletic last weekend, Parkinson's men visit the capital to face the Lions four games unbeaten in the league.
Neil Harris' Londoners are on a good run of form themselves lately, however, and Parkinson was in the crowd to see Millwall defeat Doncaster Rovers at The Den on Tuesday night to move just outside the Play-Off places.
Parkinson said: "It is always good to go down to a game and actually get a feel for the environment there.
"My job now is to make sure the knowledge I've gained from the trip is passed onto the players so they know what to expect when we get down there.
"It will be a tough game - Doncaster started slow on Tuesday night and they were punished for it.
"We are in a run of games against sides who came down from the Championship last season - Wigan, Millwall, Blackpool - and this little period will be a good benchmark for us.
"Our away form in general has been good so far this season but I think this will probably be our toughest challenge to date.
"We have been pleased with the resiliency and determination shown by the players in recent weeks but we are going to need to take it up another step on Saturday.
"I am looking forward to seeing the players out there this weekend because the game will be a good indicator again as to the strength of the group."
The fit-again duo of Billy Clarke and Josh Morris are both back in contention for this weekend after their recent return to full training.
Joe Cracknell is also expected to make the journey south with the squad after being recalled from his loan spell at Scarborough following the departure earlier this week of Brad Jones.
Tony McMahon (calf) and Billy Knott (swelling to the knee) are doubts for the game, whilst Kyel Reid had tonsillitis earlier in the week.
Parkinson added: "Both Billy and Josh will be back involved, which is great news.
"They have both trained well this week and they will certainly add to our options for the game.
"We wish Brad all the best going forward. Unfortunately his move here hasn't worked out for both parties but we have managed to get Joe back from his loan at Scarborough.
"Billy got a whack on his knee against Wigan last Saturday. He carried on with it but he got some swelling there in the early part of the week.
"He was better this morning but he hasn't training this week as of today (Thursday) so we'll have to look at that.
"Billy is playing well and he is keen to keep playing so we'll have a look at that in the (Friday) morning.
"Tony McMahon also got a whack on his calf in that (Wigan) game and that isn't right just yet. He couldn't train today.
"Reidy has had tonsillitis during the early part of the week but he has back in today.
"We know going to Millwall, we are going to have to pick a team that is physically ready to play their part.
"We won't be able to carry anyone down there.
"As a group of staff, we will be looking at the squad, assessing the injuries, and making sure we don't put anyone out there who we don't think is ready to go."