[Buffbenj]

I have potassium silicate powder. It is K20 32.4%
SiO.52.8%
I wish to make 946ml. of solution from this powder which is 3% soluble potash (K20).  (& hopefully approximately 7.8% silicon dioxide) How many grams of powder to dissolve in warm, distilled water?
3gm/100ml = 32. 4gm/x
x=1080ml. So somewhere around 30 gm is a reasonable guesstimate.
32.4gm/1080ml = x/946ml
x=28.4 gm of powder

[AWK]

Nonsense rough guesswork.
Data on the type of concentration percentage and possible density of the solution are missing.
You have a solid potassium silicate with a SiO₂:K₂O weight composition of ~1.6 and an oxide content of ~85%.
A 3% solution of K₂O will be an almost 8% solution of anhydrous silicate. The density of this solution (I guess) will be around 1.1 or a little less. This gives you over 3 times the mass of potassium silicate than you wrongly estimated.
The calculations are so specialized that your laboratory probably has tables of the density of solutions of such potassium silicate and then you can calculate it a little better.