1) The court would issue a judgement for Twitter, against Musk, for $44b.

2) Musk would either voluntarily pay it by selling his own assets, or he would refuse. If he refuses, then:

3) Twitter would go about seizing and selling Musk's assets, until they have raised funds to cover the $44b judgement.

Twitter could levy whatever brokerage or account Musk uses to hold his shares. Somewhere there is an account which records the shares. Twitter would serve the entity managing the account with a levy, and order the shares be liquidated.