shaking while driving, is this might be the problem , pix inside

[Killa]

car is shaking back and forth while driving, and other day I change my tranmission fluid, and saw those 2 bolt is loose, I tight 1 up, and other one just really loose, I dont know what this part is, it right next to tranmission pan . 1995 mustang gt automatic

 

[toyman]

Looks like the transmission mount-to-crossmember nuts.

 

[Killa]

where I can buy this part ?

 

[toyman]

I think we are talking about different things. Can you circle the bolts/nuts that were loose in the picture and post it again?