Here are some great games to practice using number lines to help us estimate

https://www.topmarks.co.uk/Flash.aspx?f=NumberLinev5

https://mathsframe.co.uk/en/resources/resource/37/placing-numbers-on-a-number-line

https://mathsframe.co.uk/en/resources/playgame/36

https://mathsframe.co.uk/en/resources/resource/266

https://mathsframe.co.uk/en/resources/resource/37/placing_numbers_on_a_number_line