Your wheelchair or scooter should have a two piece wheel (also called a split rim, imagine halving a yo yo). Since a foam filled tire is basically a pneumatic tire filled with foam during the manufacturing process, tire sizing is the same.
However the bead width of the split rim can vary. The bead width is the distance between the inside of the rims lip, where the edge of the tire seats.
This is because there was never standard (split rim) bead width sizing adopted in the wheelchair/scooter industry. As a result you can have several tires of the same size with different bead widths and only one of them will properly fit your split rim. If the bead width is too wide, you will never get the two halves of the split rim and the tire screwed back together. Check out Solid tire install tool.
The item "Pair of (2) Invacare Wheelchair M94 14 X 3 3.00 8 Solid Drive Tires new" is in sale since Friday, September 14, 2018. This item is in the category "Health & Beauty\Medical & Mobility\Mobility/Walking Equipment\Mobility Scooters". The seller is "garagepurge" and is located in Orlando, Florida. This item can be shipped to United States.