transmission will not go into gear

Is it an Auto trans or manual?

Manual- It will be the linkages most likely and you will need a mechanic if not able to do it yourself

Auto- First off check transmission oil level. If low top it up, if dirty and old drain, flush and refill. If this does not fix your problems then off to the Mechanic. If you are going to do any of this yourself and have not done it before. Chock the wheels and do not crawl under the vehicle if it is ONLY on a jack and also on flat surface