I can't see the age of the house mentioned, but lead suggests old.
In older houses I've known, the water supply pipe usually runs in a straight line from the watermain under the pavement, to where the kitchen sink used to be when the house was built. In terraced houses this tends to be under the hallway, but sometimes the pipe enters at the back.
There usually is, or was, an external stopcock in the ground next to where the front gate used to be when the house was built. Sometimes in the pavement, sometimes in the garden beside the path, sometimes both.
Ignorant buffoons often pave over the access to the stopcock. If you look at neighbours similar houses, you can form an opinion about possible stopcock locations. You may need to dig a hole. The pipes commonly start leaking after 60 to 100 years.
You mention you are going to replace the pipe, so I strongly recommend having a full-bore external stopcock, at or near the boundary, so close to the watermain, and an internal one where the pipe rises out of the floor, commonly under the sink. In the unlikely event of damage or a leak, this will enable you to isolate either your external pipe run, or the internal plumbing. Some people fit a cheaper 15mm stopcock, which will restrict the flow somewhat. You can tee off to a garden tap at the external stopcock if you like. The new pipe does not have to follow the same route as the old. You can add modern insulation where the pipe is exposed.
Several times I and my family had frozen or burst pipes. An easily accessible external stopcock enabled neighbours, and in one case police, to turn off the supply.
As you are replacing lead, there might be a subsidy or free connection from your water company. Apply before you start work. You might need to have your drinking water tested for lead (free) first.
