"We should study."
Translation:हमें पढ़ना चाहिए।
पढ़ने is the masculine plural and also the oblique form of the infinitive पढ़ना.
As the plural form, it is used when it has a masculine plural object. Eg: हमें दोनों अख़बार पढ़ने है (We have to read both the newspapers).
As the oblique form, it is used when the infinitive is the object of a postposition. Eg: मैं पढ़ने से पहले कुछ देर खेलूँगा (I will play for a while before studying).
It is also used when the infinitive is an object of the intransitive verbs आना and जाना where the postposition is dropped but is still assumed to be present for grammatical purposes ('ghostposition'). Eg: मैं अब पढ़ने जा रहा हूँ (I am going to study now).