It is bit heavy and it is almost 8 inches tall. What type of conch is this? Can we use it to blow or do we keep it in the puja?
As per the shared picture, It is right handed conch. It is also known as Sri Lakshmi conch and used for worship.
Quoting from the article "The role of Conch in Hindu Gods"
There are two types of Shankh – left handed conch shell and right handed conch shell. Valampiri Shankh or Lakshmi Shankh is the right handed conch shell and is considered auspicious.
The shankhas that open towards the right hand are called Dakshinavarti Shankhas. These shahkhas are rare and are available in white color with brown lines on them that run towards the right or South. Lord Kuber (God of wealth) resides in South and so this shankha represents wealth and prosperity. Shankha is blown at every festival and auspicious beginning and the sound ushers in freshness and new hope. Right handed conch shell is kept at home by many people as it is believed to bring wealth and prosperity. It is also associated with Kubera, god of wealth. Many institutions and organizations employ conch shell as their symbol.
Quoting from same article on how to use it for worship:
Usually, right handed conch shell is used for worship. The shell is thoroughly cleaned and is placed on a clean cloth, usually red , white or yellow cloth. Normal puja is performed. In some places, conch shell is placed on a silver or clay pot. A cloth is used to cover the mouth of the pot and it is placed on it.
People usually collect and keep water in conch shell and is sprinkled while performing pujas. While performing Lakshmi Puja, conch shell is filled with milk and then it is poured over the idol. Water collected in Shankh with Holy Ganga water, banana, china rose flower and atap rice - is offered while worshipping sun.