Id like to ask for help in fixing the missing values in pandas dataframe (python)

here is the dataset
[![dataset](https://i.stack.imgur.com/RVkMA.png)](https://i.stack.imgur.com/RVkMA.png)

In this dataset I found a missing value in ['Item\_Weight'] column.

I don't want to drop the missing values because I found out by sorting them. the missing value is "miss type" by someone who encoded it.

here is the sorted dataset
[![sorted_dataset](https://i.stack.imgur.com/MPpKi.png)](https://i.stack.imgur.com/MPpKi.png)

Now I created a lookup dataset so I can merge them to fill na missing values.

[![Lookup Table](https://i.stack.imgur.com/ExVlA.png)](https://i.stack.imgur.com/ExVlA.png)

How can I merge them or join them only to fill the missing values (Nan) using the lookup table I made? Or is there any other way without using a lookup table?