Connection between Embedding and LSTM and Dense layer
The embedding layer has an output shape of 50. The first LSTM layer has an output shape of 100. How many parameters are here? Take a look at this blog to understand different components of an LSTM layer.

Then you can get the number of parameters of an LSTM layer from the equations or from this post. 

Now, between LSTM(100) layer and the Dense(100, activation='relu') layer, there should be 100*(100 + 1) parameters. The additional 1 is for the bias.