Once you reach Memphis, do NOT take the I-55 bridge across into Arkansas. Rather continue straight and I-55 literally turns into Front St. Go onwards down the hill and about 3 miles ahead you will see the Tennessee Welcome Center. You should have lots of room to park your RV and plz plan on spending at least some time in Memphis as there is lots to see and do...not to mention some of the best BBQ in my opinion.
Have a safe trip!
Once you've had your fill, cross the I-40 bridge and you'll be reconnected back with I-55.