As far as I know TAENIA SOLIUM is an acoelomate which basically means that the space between the alimentary canal and the gut is completely filled [or] occupied by the mesoderm and they do not have primary body cavity as well as secondary body cavity then from where does the space comes in taenia to store that huge amount of eggs
The eggs are very small compared to the proglottid.
According to this site:
T. saginata can be up to 4 to 6 meters long and 12 mm broad; it has a pear-shaped head (scolex) with four suckers but no hooks or neck. It has a long flat body with several hundred segments (proglottids). Each segment is about 18 x 6 mm with a branched uterus (15-30 branches). The egg is 35 x 45 micrometers, roundish and yellow-brown. It has peripheral radial striations and contains an embryo with 3 hooklets.
T. solium is slightly smaller than T. saginata. It has a globular scolex with four suckers and a circular row of hooks (rostellum) that gives it a solar appearance. There is a neck and it has a long flat body (0.1 meter in length). The proglottids are 5 x 10 mm with a 7-12 branch uterus. The eggs of T. solium and T. saginata are indistinguishable.
I assume that the measurements given for the T. solium proglottid relate to the dimensions of your diagram, and since this is a tapeworm it is thinner than either of these values, so let's assume 2 mm to make the arithmetic easy.
volume of proglottid = 5 * 10 * 2 * 10-9 = 100 * 10-9 = 10-7 m3.
The egg approximates to a 40 µm sphere = 33,500 * 10-18 m3
So, volume of 35,000 eggs = 1.2 * 10-9 m3
So, volume occupied by eggs = (1.2 * 1010-9 * 100)/1010-7 % of proglottid = 1.2 %
So, not much of an accommodation is required for the volume of the eggs, even allowing for errors in this approximation (e.g. I neglected spherical packing which would add somewhat to the volume occupied by the packed eggs).