１．単位
1 Ether = 1,000,000,000,000,000,000 Wei
1 Ether = 1,000,000,000 Gwei
1 GWai = 1,000,000,000 Wei

https://www.investopedia.com/thmb/XqqZp7mA1vGnK5DwIdfidNLuTIw=/660×0/filters:no_upscale():max_bytes(150000):strip_icc():format(webp)/dotdash_INV_final_Gwei_Ethereum_Jan_2021-01-370e27f6becf4830b333dacffe739415.jpg

２．nodeでの変換
例 )

 balanceWai = web3.eth.getBalance(web3, coinbase) ;

 balanceGwai = web3.utils.fromWei(balanceWei, 'Gwei');
 balanceWai = web3.utils.toWei(balanceGwei, 'Gwei');