The missing material from your list is a solvent, specifically water (preferably distilled water). This is necessary because to test the ionic nature of a compound, you need to dissolve it in a solvent. Ionic compounds typically dissociate into their respective ions when dissolved in water, allowing you to test the conductivity of the resulting solution.
Conductivity can be measured with the conductivity apparatus to determine if the compound produces ions that are free to move and carry an electric current. If the solid compound is ionic, it should dissociate and produce ions in solution, leading to a measurable increase in conductivity. Without water or another suitable solvent, you won't be able to properly assess the compound's ionic nature.