Multiply the dimensions of your tank and then divide into 1000. So you'll calculate estimated volume (in liters) of your tank (which includes water, filters, sand, stones, etc)
For an ex : Guess your tanks dimensions are like 50 cm (w), 40 cm (h) and 30 cm (d)
Calculation : 50x40x30 = 60.000/1.000 = 60 lt.
Healthy tropical fishes needs net 5 lt (minimum) of water in a tank. You wrote, you bought 10 fishes, that means you need a tank, which you may fill net 50 lt of water (minimum). Please check yours.
On the other side, the tiger barb is a lively, playful fishes which should be kept in groups of seven or more. They may become aggressive and may harass others. Mollies are peaceful, attractive tropical fish that thrive on almost any type of fish food presented to them. I may say that your fishes are not suitable fishes for living together.
Facebook groups link is facebook.com/groups/103615099824897/ .
As an advise, never buy artificial things for your aquariums (plant, sand, stones, etc.). They are colored by chemicals which may poison your fishes. Always choose naturals.