Wondering if you know that. I checked https://jochen-hoenicke.de/queue/#1,24h and it gives interesting stats for pending transactions and fees. But I have never heard of mempool in ethereum ecosystem.
Yes Ethereum has a mempool which consists of all pending transactions. You can check this on etherscan. It should be noted that transactions in Ethereum can be very different: a simple Ethereum transfer costs 21000 gas units, while a large contract call can take over 7 million units. To create such mempool for Ethereum I think the sum of all pending transactions gas limits should be calculated.
Ethereum is having a txpool in which transactions are kept (see here for a nice discussion of limits), that have not been mined yet.
In geth, you can inspect that txpool via
txpool and if you just want to get the number of pending transactions you can do