小学三年级英语单词和句型的要求会因不同的教学大纲、教材和学校而有所不同。一般来说，以下是一些可能需要掌握的单词和句型：

单词：
- 常见的动词，如run, jump, swim, eat, drink, sleep等
- 常见的名词，如book, pencil, bag, teacher, student等
- 常见的形容词，如big, small, happy, sad, tired等
- 常见的副词，如fast, slow, well, badly等
- 一些数字和基本的时间词，如one, two, three, four, five, six, seven, eight, nine, ten, Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday等

句型：
- 简单的陈述句，如I am a student. She likes to read books. They play soccer on weekends.
- 简单的疑问句，如Do you like ice cream? Can you swim? Is he your friend?
- 简单的否定句，如I don't like vegetables. She isn't happy today. They didn't go to the park yesterday.

需要注意的是，这只是一个大致的参考，具体的要求还需要根据实际情况而定。同时，语言学习是一个渐进的过程，掌握的单词和句型数量并不是最重要的，更重要的是能够正确地运用所学的知识。