Return to Running After Illness

Hi everyone! I trained for and completed the Philadelphia Marathon (end of November) but have not run consistently since. I took a scheduled 2 weeks off after the marathon, ran for 2 weeks after the break consisting of some easy low mileage, then caught pneumonia and was benched for almost 2 months. I have been doing strength training and running just a mile on the treadmill 2-3x a week the last month to ease back into fitness. I finished my first full week of running and am starting a training block for a 10 mile race. My question is where do I start from? I am unsure how long it will take me to bounce back after 2 months off so I don't know what pace to use for speedwork and things of that sort. Do I need to start from scratch when it comes to building up mileage? Thank you!