"Build upon" is the same as "build on". The Cambridge Dictionary definition is this: build on : to use a success or achievement as a base from which to achieve more success In other words, you already have some strengths, and you use these strengths as a starting point for further success. For example, if communication is one of your strengths, you should make the most of this ability and develop it further in order to help you get on in life. This is not the same as 'build up' : 'build up' means increase or strengthen over time. We normally talk about building up a person's strength (in the uncountable sense) when they increase their health and fitness. If someone has been ill, they need to build up their strength by eating nutritious food and taking exercise.

In that specific example sentence, they would mean basically the same thing, yes. They have slightly different meanings though, and cannot always be used interchangeably. ‘Build upon’ is equal to ‘build on’ (which might be easier to find in a dictionary) so the difference comes down to the difference between ‘up’ and ‘on’. ‘Build on’ or ‘build upon’, implies that there is already something there to be built on, e.g. ‘The house was built upon a foundation’, ‘I look forward to the opportunity to build on my success’. ‘Build up’ just means to increase, so there may or may not be something already there to increase, e.g. ‘They will need to build up more speed’, ‘The movie really built up suspense’.

The idea is similar, but the object of 'to build upon' is something that you already have which you can use to develop something else. The object of 'to build on' is the thing that you want to develop. Build upon: "You can develop more advanced skills by building upon what you already know." "You can develop further by building upon the strengths that you already have." Build up: "You can build up skills by practicing them everyday."

The other comments have pretty much answered the question, but here's a simplified version just in case. 1. build up – increase in size or quality 2. build upon – to build "on" something e.g. 1 Damn, I really need to build up my confidence. e.g. 2 We'll start with an outline of the project so that later we have something to build upon.