That will not detect an alpha emitter as alphas will not penetrate the metal casing of the film canister. Alphas and very low energy Betas can be very difficult to detect. However, they will not penetrate the dead skin cells on the surface of your skin, let alone normal clothing so they are also a minimal hazard UNLESS the material is heated, ground, cut, or otherwise handled in some way as to send particles airborn where they may be inhaled.
Most survey meters will not detect alphas or low energy betas as to do so requires a very low density, and therefor fragile window. Historically, extremely thin slices of mica were used for the windows on alpha detectors.
If you think or suspect that you are in posession of radioactive material inappropriate for consumer use please call your state EPA or even your local fire or police department. They may not be equipped to test the material but they should know whom to contact.