Hi, Rajashree!
Being a popular tourist destination now, finding a quiet place with great view in Mussoorie might be difficult. However, if you are ready to explore some places close to Mussoorie like Kanatal, Dhanaulti, and Clouds End, you will very easily find secluded accommodations with great views. For more such options, you may check out the following link: https://www.tripoto.com/hotels/Mussoorie-Hotels-That-Are-Perfect-Hideaways
Hey, you can look for accomodation at landour (if you have a good budget, try rokeby manor). you can also try hotels at barlowganj (it's pretty much secluded).
Landaur and Barlowgunj are good locations. A little away from Mussoorie, not so crowded, and amazing views. Also the hotel rates might turn out to be less than at Mall Road or Mussoorie Town.